AVS 62nd International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM+MS-ThA

Paper EM+MS-ThA6
Tuning Bandgap Through Cation Ordering in New PV Materials

Thursday, October 22, 2015, 4:00 pm, Room 210E

Session: III-N Nitrides II
Presenter: Steve Durbin, Western Michigan University
Authors: S.M. Durbin, Western Michigan University
R.A. Makin, Western Michigan University
N. Feldberg, Western Michigan University
J.P. Mathis, University of Michigan
N. Senabulya, University of Michigan
R. Clarke, University of Michigan
Correspondent: Click to Email
There continues to be considerable interest in so-called earth abundant element compound semiconductors, of which we have multiple candidates at present. One material worth considering, ZnSnN2, is properly termed a ternary heterovalent compound and is a member of the more general family of II-IV-V2 semiconductors. It is analogous to InN, whereby pairs of indium atoms are replaced by a periodic arrangement of a Zn and Sn atom, and in that way is related to CIGS as that material corresponds to II-VI semiconductors. Although ZnSnN2 is predicted to crystallize in an orthorhombic lattice with a bandgap of approximately 2.0 eV (calculations reported in the literature vary somewhat), we have observed that single crystal thin films grown by plasma-assisted molecular beam epitaxy are more likely to form in a wurtzitic lattice, with a lower electronic bandgap energy. In fact, we have recently observed both optical absorption and x-ray emission spectroscopy results on a series of films which agree with density functional theory calculations predicting a bandgap as small as 1 eV - the direct consequence of disorder in the cation sublattice. Careful tuning of the growth parameters enables the degree of order to be varied, and consequently the bandgap energy as well. This provides the intriguing possibility of tuning the bandgap through the growth process, as opposed to the traditional approach of alloying. The optimal bandgap energy of approximately 1.5 eV would therefore be an intermediate state between the two extremes.